A conventional sport racket generally includes a post-like shaft with a handle connected to one end and a frame on the other end of the shaft. The frame generally includes a netted area so that the balls bounce back when the users hit the balls by the netted area of the sport racket. These kinds of sport rackets include tennis rackets, badminton rackets and squash rackets.
The netted portion of the rackets includes a sweet spot which is an area on the netted portion and can apply the force of swing to the center of the balls so as to deliver the balls with power and accuracy. There are many skills for the user to send the balls by using the netted portion and the key purpose is to send the balls to the expected position as desired force, speed and distance.
It is noted that the conventional strings for sport rackets generally includes a circular cross section with smooth outer surface which reduces friction between the strings and the balls so that the balls cannot be controlled easily. The conventional strings are made of Nylon, natural gut intestine string, artificial gut intestine string, or artificial fibers.
An improved string known to applicant includes a center core and a first layer wrapped around the outer surface of the center core. The first layer provides improved friction between the strings and the balls. However, the when stringing the strings to the frame, the strings wear out due to mutually contact between the strings. The strings can not be last long.
The present invention intends to provide a string of a sport racket and the string includes recesses defined in an outer surface of the string so as to increase the friction between the strings and the balls.